This event occurs in Hard Mode after defeating Golem. It is triggered by defeating the Ancient Cultists that spawn at the entrance to the Dungeon, and then killing the Lunatic Cultist, which appears after all 4 of the Ancient Cultists are dead.

Boss Minions

Coin Drops

Enemy Coin drops are calculated from set values in the game code, but in-game have an unstated variable factor that is multiplied onto that value every time those coins are dropped. For example; the Dungeon Slime is set to drop 1 50 , but would in reality drop that or anything around that amount. The same rule applies with Pinky, being set to drop 1 but dropping that or anything a little over or a little under that. This rule applies to all NPCs that drop coins.